The present invention relates to a carbon fiber composite material in which carbon nanofibers are uniformly dispersed, and a method of producing the same.
In general, it is difficult to disperse carbon nanofibers in a matrix as a filler. The inventors of the invention have proposed a method of producing a carbon fiber composite material which improves the dispersibility of carbon nanofibers to enable the carbon nanofibers to be uniformly dispersed in an elastomer (see JP-A-2005-97525, for example). According to this method, an elastomer and carbon nanofibers are mixed to improve the dispersibility of the carbon nanofibers with strong aggregating properties due to a shear force. More specifically, when mixing an elastomer and carbon nanofibers, the viscous elastomer enters the space between the carbon nanofibers, whereby a specific portion of the elastomer bonds to a highly active site of the carbon nanofibers through chemical interaction. When a high shear force is applied to the mixture of the elastomer having an appropriately long molecular length and a high molecular mobility (exhibiting elasticity) and the carbon nanofibers, the carbon nanofibers move along with the deformation of the elastomer. The aggregated carbon nanofibers are separated by the restoring force of the shorn elastomer due to elasticity, and become dispersed in the elastomer.
The inventors have also proposed a method of producing a carbon fiber-metal composite material in which carbon nanofibers are uniformly dispersed in a matrix such as a metal matrix using a carbon fiber composite material in which carbon nanofibers are uniformly dispersed (see JP-A-2005-97534, for example).
As described above, expensive carbon nanofibers can be efficiently used as a filler for a composite material by improving the dispersibility of the carbon nanofibers in the matrix.